The freezing of samples, in particular under high pressure, is a widely used method for preparing samples, for example for viewing under an electron microscope. This high-pressure freezing makes it possible to view water-containing biological and industrial samples in close to their original state. For example, freezing at pressures of approximately 2000 bar suppresses the formation of ice crystals and avoids structural damage to the sample. The process is referred to as “vitrification,” i.e. the solidification of a liquid by elevating its viscosity while it is being cooled: crystallization is absent, and an amorphous material thus results. This is achieved by extremely rapid cooling (e.g. in liquid nitrogen), usually in interaction with additives that prevent crystallization (called “cryoprotectives”).
Freezing machines, in particular high-pressure freezing machines, that are used for the above-described freezing of samples are obtainable. These freezing machines do make it possible to freeze a sample, but the problem of further handling then arises, since the cold chain should if possible not be interrupted.
A freezing machine is available from the Applicant under the designation “Leica EM HPM100”; it encompasses for this purpose a container, cooled with liquid nitrogen, into which the samples are automatically introduced after the freezing operation. This does initially allow the cold chain to be ensured, but there is no possibility of sorting or tracking samples introduced into the container. Freezing of different samples in series is thus not possible or possible only with additional outlay.
A further problem that results in the context of freezing in series is that the supply of liquid nitrogen present in the container may not last until the end of the series. The series may therefore need to be interrupted in order to refill the container with liquid nitrogen.
The object that presents itself is therefore that of describing a capability for allowing simple execution even of longer series of freezing operations of samples, in particular also including different samples.